[Wien] ghost bands

[Dr. B.R.Sahu]

Dear W2k users

      I had sent a query regarding ghost bands in supercell calculation
few days ago. If any user have some suggestions, It would be helpful.If
you need any more information than provided pl. let me know.

 I have a supercell of K host + one Ti 
 with distance of the Ti from first K shell , d(K-Ti)=8.01 au.  In this
 run, I had set
 d(K-Ti)=5.0 au  to begin with (ie RMT=2.5 for K and Ti each)  
 and the calculation converged without any ghost bands(u-dot 
 contribution smaller than u).

 I wanted to increase the RMT of K and Ti to 4.0 a.u each so that they
 almost touch each other ie d(K-Ti)=8.0 au. I started the calculation all
 over from scratch. This time the calculation is faster than the previous
 run(due to small number of plane waves in the interstitials) but I get the
 QTL-B value very large ie
 
 QTL-B VALUE .EQ.   32.30382   !!!!!!
 
 I understand that such a large value for QTL-B is indeed ghost band
 signature in the scf calculation.
 
 The parameters used for both runs are SAME:
 
 RKMAX= 8.0
 
 Number of k-points in IBZ = 120( a dense mesh is not needed for such a
 large cell but I believe it is not one of the reason for appearance of
 ghost band).
 
 Unit cell size = about 20 au.
 
 RMT(Ti)=2.5 and RMT(K)=2.5 in the first case(NO GHOST BANDS).
 
 RMT(Ti)=4.0 and RMT(K)=4.0 in the second case(GHOST BANDS).
 
 Is RKMAX=8.0 is large enough to cause ghost bands?
 
 Here is the case.in1 file:
 
 _______________________________________________________________________________
 WFFIL        (WFPRI, SUPWF)
   8.00       10    4 (R-MT*K-MAX; MAX L IN WF, V-NMT
   0.30    4  0      (GLOBAL E-PARAMETER WITH n OTHER CHOICES, global 
 APW/LAPW)
  0   -2.29      0.010 CONT 1
  0    0.30      0.000 CONT 1
  1   -1.07      0.010 CONT 1
  1    0.30      0.000 CONT 1
   0.30    4  0      (GLOBAL E-PARAMETER WITH n OTHER CHOICES, global 
 APW/LAPW)
  0   -2.29      0.010 CONT 1
  0    0.30      0.000 CONT 1
  1   -1.07      0.010 CONT 1
  1    0.30      0.000 CONT 1
   0.30    4  0      (GLOBAL E-PARAMETER WITH n OTHER CHOICES, global 
 APW/LAPW)
  0   -2.29      0.010 CONT 1
  0    0.30      0.000 CONT 1
  1   -1.07      0.010 CONT 1
  1    0.30      0.000 CONT 1
   0.30    4  0      (GLOBAL E-PARAMETER WITH n OTHER CHOICES, global 
 APW/LAPW)
  0   -2.29      0.010 CONT 1
  0    0.30      0.000 CONT 1
  1   -1.07      0.010 CONT 1
  1    0.30      0.000 CONT 1
   0.30    5  0      (GLOBAL E-PARAMETER WITH n OTHER CHOICES, global 
 APW/LAPW)
  0    0.30      0.000 CONT 1
  0   -4.35      0.005 STOP 1
  1   -2.58      0.010 CONT 1
  1    0.30      0.000 CONT 1
  2    0.30      0.010 CONT 1
 K-VECTORS FROM UNIT:4   -9.0       2.5      emin/emax window
 _______________________________________________________
 
 
 where I am going wrong?pl. suggest.
 
 best regards
 sahu